Benefits of Plant Growth-Promoting Rhizobacteria and Rhizobia in Agriculture

Isolation of plant growth-promoting rhizobacteria from the agricultural fields of Tattiannaram, Telangana

BACKGROUND

Plant probiotics bacteria are live microbes that promote soil health and plant growth and build the stress-tolerant capacity to the plants. They benefit the plants by increasing nutrient absorption and release of stress-related phytohormones. These plant probiotic bacteria serve a better purpose to the plant when compared to chemical fertilizers. Use of chemical fertilizers such as arsenic and cadmium can lead to soil acidification and even release of harmful gases such as methane which further pollutes the environment.

RESULTS

Different bacterial species were isolated from the agricultural fields of Tattiannaram, Telangana, and identified as the efficient rhizosphere bacteria with the essential qualities of plant growth promotion by evaluating the nitrogen-fixing ability on a selective media and various other methods. Upon the molecular characterization of the isolates, they were identified as Corynebacterium spp., Bacillus spp., Lactobacillus spp., and Cytobacillus spp. The results were also examined using various bioinformatics tools for accuracy in their phylogenetic pattern.

CONCLUSION

The recognized species of plant probiotics have established roles in promoting plant growth and strengthening plant immunity. This research introduces an innovative methodology for evaluating and investigating recently identified bacterial isolates, focusing on their distinctive plant probiotic attributes. Through harnessing the potential of advantageous microorganisms and comprehending their interaction with plants and soil, our objective is to formulate inventive approaches to elevate crop productivity, enhance soil richness, and foster environmentally sustainable and robust agricultural methodologies. These characteristics exhibit promising potential for future incorporation into plant systems, fortifying growth and development, and underscoring their distinctive significance within the realm of agriculture.

Soilborne bacterium Klebsiella pneumoniae promotes cluster root formation in white lupin through ethylene mediation

Cluster roots of white lupin are induced by low phosphorus (LP) to efficiently access unavailable P, but how soilborne microbes are associated with cluster root formation (CRF) is unclear. We investigated the roles of soilborne bacteria in CRF response to LP by high-throughput sequencing and root-bacteria interactions. Cluster root number was significantly decreased in plants grown in sterilized soil compared with nonsterilized soil. Proteobacteria was enriched in CR, as shown by microbiome analysis of soil (bulk, rhizosphere, and rhizosheath) and roots (main, lateral, and CR). Large-scale gene expression level implicated ethylene mediation in CRF. Klebsiella pneumoniae (P7), a soilborne bacterium belonging to Proteobacteria, was isolated from CR. Among 11 isolated strains, P7 exhibited the highest 1-aminocyclopropane-1-carboxylate deaminase (ACCD) activity; this enzyme inhibits the biosynthesis of ethylene in plants by the cleavage of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid and promotes CRF under LP. We constructed an ACCD-deficit mutant accd in the P7 genetic background. The loss-of-function mutation failed to promote CRF under LP conditions. Also, auxin responses may be involved in K. pneumoniae-ethylene-mediated CRF. Overall, we propose that the soilborne bacterium K. pneumoniae promotes CRF of white lupin in response to LP by ethylene mediation.

Bacterial diversity changes in response to an altitudinal gradient in arid and semi-arid regions and their effects on crops growth

The microbiome of soil has a fundamental role in maintaining the health of soil and plants. While the diversity of microbes is one of the most important factors in the environment, little is known about the effects of elevation on the microbiome and the impact of the affected microbiome on plants. The main goal of this study is to expand our knowledge of what happens to the soil bacterial community along an altitudinal gradient and investigate their possibly different impacts on plant growth. Bacteria from soils at various altitudes have been isolated, characterized, and identified by Matrix-Assisted Laser Desorption/Ionization-Time of Flight Mass Spectrometry (MALDI-TOF MS) to determine the effects of an elevational gradient on the microbiome and plant growth. Furthermore, their effects have been investigated by isolates assessment on maize, wheat, and canola. Based on our results, higher altitude results in a higher diversity of the microbiome and lower bacteria biomass. Bacillus cereus is found in abundance in arid and semi-arid samples. Interestingly, enhanced diversity in higher altitudes shows similarity in response to environmental stress and tolerates these factors well. Furthermore, the inoculation of these bacteria could enhance the overall growth of plants. We prove that bacterial communities could change their biomass and diversity in response to altitude changes. These indicate evolutionary pressure as these bacteria could tolerate stress factors well and have a better relationship with plants.

Development of Banana Peel Powder as Organic Carrier based Bioformulation and Determination of its Plant Growth Promoting Efficacy in Rice Cr100g

Agriculture is the primary source of income for more than 50 % of the Indian population and the current challenge in the agricultural industry is the increased crop production with sustainable agricultural practices from the shrinking cropland area. Plant Growth Promoting Rhizobacteria (PGPR) has been used as a bio inoculants for increasing the crop yield and the effectiveness of PGPR as biofertilizers majorly depends on the selection of the best carrier material, proper formulation of microorganisms and mode of delivery of the formulation. So, the present study investigates the effect of PGPR bacterial strains isolated from the Siruvani forest region, Coimbatore, Tamil Nadu. We have tested the efficacy of these PGPR strains using both in vitro seed germination assay and in vivo pot culture studies in CR100G rice seeds. We have used the banana peel powder (Patent No: 202041010982) as a novel organic carrier material for the development of bioformulation, along with talc as an inorganic carrier material to perform the in vivo study. The results showed that the rice plants treated with banana peel powder based bioformulation gives the highest shoot length (15.78 cm) when compared to the control (10.48 cm) on the 14th day, 21st and 45th day of seed seeding. The grain yield also increased in the Non-Enriched Banana Single (NEBS) bacterium group (125%) when normalized with the control. Thus, our current study suggests that Banana peel powder could be the better approach to be used as an organic carrier material for the development of Biofertilizers in future.

Nanotoxicity of engineered nanomaterials (ENMs) to environmentally relevant beneficial soil bacteria - a critical review

Deposition of engineered nanomaterials (ENMs) in various environmental compartments is projected to continue rising exponentially. Terrestrial environments are expected to be the largest repository for environmentally released ENMs. Because ENMs are enriched in biosolids during wastewater treatment, agriculturally applied biosolids facilitate ENM exposure of key soil micro-organisms, such as plant growth-promoting rhizobacteria (PGPR). The ecological ramifications of increasing levels of ENM exposure of terrestrial micro-organisms are not clearly understood, but a growing body of research has investigated the toxicity of ENMs to various soil bacteria using a myriad of toxicity end-points and experimental procedures. This review explores what is known regarding ENM toxicity to important soil bacteria, with a focus on ENMs which are expected to accumulate in terrestrial ecosystems at the highest concentrations and pose the greatest potential threat to soil micro-organisms having potential indirect detrimental effects on plant growth. Knowledge gaps in the fundamental understanding of nanotoxicity to bacteria are identified, including the role of physicochemical properties of ENMs in toxicity responses, particularly in agriculturally relevant micro-organisms. Strategies for improving the impact of future research through the implementation of in-depth ENM characterization and use of necessary experimental controls are proposed. The future of nanotoxicological research employing microbial ecoreceptors is also explored, highlighting the need for continued research utilizing bacterial isolates while concurrently expanding efforts to study ENM-bacteria interactions in more complex environmentally relevant media, e.g. soil. Additionally, the particular importance of future work to extensively examine nanotoxicity in the context of bacterial ecosystem function, especially of plant growth-promoting agents, is proposed.